Recently there have been Payload threads with sketches using SketchUp, this makes your sketch incredibly clean and good looking.
You can download SketchUp here: http://sketchup.google.com/
After you have downloaded and installed it open it up.
Before we start, you need to know the most important tools in SU (SketchUp)
Line tool - Draws lines
Rectangle tool - Draws rectangles (duh)
Circle tool - Draws circles
Arc tool - Like the line too except it draws arcs
Eraser - Removes lines and arcs
Paint Bucket tool - Paints surfaces with different textures
Push/Pull tool - Stretches and scales draws
Move/Copy tool - Move lines
Orbit tool -Let's you change your view
Pan tool - Let's you Navigate around in 3D
Just be careful because Hammer is not compatible with all the shapes you can make in SketchUp. (Also if you think you can just convert someone else model into hammer, think aging because almost all of it will be invalid geometry.)
Pros: Very clear tutorial. This tutorial brought a new tool to my awareness, and an awesome tool at that. You are very clear in your descriptions of the different tools and you give a fairly decent run-through of the basics.
Cons: As much as I hate to say it, this tutorial is way too short.
Improvements: Show us some more stuff about this tool. Its a great tool and I'm sure you can think of more stuff to add.
Overall: A great tutorial, but it leaves the reader wanting more as it is a bit too short.